Molecular models tend to fascinate. As a introduction to the chemistry of elements, students seem to like putting them together, and they tend to enjoy finding out what their molecules are called.
You can’t beat fitting together molecules by hand as a learning experience, but 3Dchem has a nice collection of interactive, three-dimensional molecules, including molecules of the month.
They also have three-dimensional periodic tables showing the sizes of the atoms in the traditional tabular form as well as a spiral.
